http://www.php.net/manual/language.expressions.php
<snip>
One last thing worth mentioning is the truth value of expressions. In many
events, mainly in conditional execution and loops, you're not interested in
the specific value of the expression, but only care about whether it means
TRUE or FALSE (PHP doesn't have a dedicated boolean type). The truth value
of expressions in PHP is calculated in a similar way to perl. Any numeric
non-zero numeric value is TRUE, zero is FALSE. Be sure to note that negative
values are non-zero and are thus considered TRUE! The empty string and the
string "0" are FALSE; all other strings are TRUE. With non-scalar values
(arrays and objects) - if the value contains no elements it's considered
FALSE, otherwise it's considered TRUE.
</snip>
Since variables doesn't need to be declared it's regarded as set when used
in an expression... hence $a is evaluated to "", or 0 if compared to
numbers, false if compared to boolean.
-Jørg
-----Original Message-----
From: Neil Zanella [mailto:[EMAIL PROTECTED]]
Sent: 10. januar 2001 19:33
To: Toby Butzon
Cc: PHP General Mailing List
Subject: Re: [PHP] PHP newbie question
On Wed, 10 Jan 2001, Toby Butzon wrote:
> : <?php if (! $a) print "Hello, World!"; // script 2 ?>
>
> $a evaluates to false, the ! reverses it, and it prints "Hello, World!"
What is bothering me is the following: if variables that are not assigned
a value were to evaluate to false then since false is the same as the
number 1 the following PHP script should print the number 1 but instead
prints nothing:
<?php if (! $a) print $a; ?>
How is this behavior justified?
I could not find anything on this in the PHP manual.
Thanks,
-- Neil
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